Method for reducing argon diffusion from high density plasma films

Abstract

A two-step high density plasma-CVD process is described wherein the argon content in the film is controlled by using two different argon concentrations in the argon / silane / oxygen gas mixture used for generating the high density plasma. The first step deposition uses high argon concentration and low sputter etch-to-deposition (E / D) ratio. High E / D ratio maintains the gap openings without necking. In the second step, a lower argon concentration and lower E / D ratio are used. Since observed metal defects are caused by argon diffusion in the top 200-300 nm of the HDP-CVD film, by controlling argon concentration in the top part of the film (i.e. second step deposition) to a low value, a reduced number of metal defects are achieved.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to a method of forming a semiconductor device, and more particularly to form defect-free metal interconnect structures with improved inter-level dielectric layers.DESCRIPTION OF THE PRIOR ART[0002]With the increase in the number of transistors on a given silicon chip, the metal interconnect structures also are becoming dense to handle the wiring requirement for these integrated circuits (IC). Chip size needs to be kept small to maintain the high speed of the IC device and to increase the number of dies per water. This is accomplished by distributing the wiring over several metal layers, the structure being usually known as multi level metal (MLM) layers. It is not uncommon to have upwards of six levels of metal layers with required number of interconnecting via between two successive metal layers.[0003]One conventional method of forming these MLM structures is deposit first level metal on a silicon water having devi...

AI Technical Summary

Benefits of technology

[0011]Another object of this invention is to describe a two-step HDP-CVD process to minimize die argon content in the top part of said gap filling inter level dielectric film in order to reduce metal defects.

[0012]In accordance with these objectives, a two-step HDP-CVD process is described wherein the argon content in the film is controlled by using two different argon concentrations in the argon / silane / oxygen gas mixture. The first step deposition uses high argon concentration and low sputter etch-to-deposition (E / D) ratio. In the second step, a lower argon concentration mid lower E / D ratio are used. By controlling argon concentration in the top part of the film to a low value, a reduced number of metal defects are achieved.

Problems solved by technology

With the increase in the number of transistors on a given silicon chip, the metal interconnect structures also are becoming dense to handle the wiring requirement for these integrated circuits (IC).

Although chemical vapor deposition (CVD) methods are suitable if filling high aspect ratio (height:gap-width) gaps have been used, they require higher temperatures>600 C. Such temperatures cannot be used since the metal wiring such as Aluminum, AlCu alloys have melting points close to these temperatures.

These methods therefore give rise to stresses in the ILD limits causing defects in metal lines that get buried in ILD films.

The prior art patents do not disclose or discuss the defects caused by the incorporation of argon atoms in the dielectric film during HDP-CVD process.

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